Bell System Voice Communications

Transcription

1 PUB Bell System Voice Communications TECHNICAL REFERENCE Functional Product Class Criteria Telephones January 1980 DIRECTOR-BUSINESS PREMISES ENGINEERING DATA AND SPECIAL Telephone & Telegraph Compa11y, 1980 PrintN1 In U,S.A. BNR INC. Information Resource Center G85A E. Middlefield Road Mountain View, CA

2 NOTICE This Technical Reference is published by American Telephone and Telegraph Company as a guide for the designers, manufacturers, consultants, and suppliers of telephone systems and equipment which are to be directly electrically connected to the Bell System telecommunications network. American Telephone and Telegraph Company reserves the right to revise this Technical Reference for any reason, including, but not limited to, :onformity with Federal Communications Commission (FCC) regulations; standards promulgated by the American National Standards Institute (ANSI), the Electronic Industries Association (EIA), or standards of other organizations and agencies; utilization of new advances in the state of the technical arts; or to reflect changes in the design of equipment or services described herein. The limits of responsibility and liability of the Bell System with respect to use of customer-provided systems or equipment are set forth in the appropriate tariff regulations. If further information is required, please write: Director - Business Premises Engineering - Data and Special Systems American Telephone and Telegraph Company 295 North Maple Avenue Basking Ridge, New Jersey 07920

3 TECHNICAL REFERENCE FUNCTIONAL PRODUCT CLASS CRITERIA TELEPHONES TABLE OF CONTENTS Page 1.0 INTRODUCTION 1. 1 Purpose 1.2 Scope 1.3 Definition of a Telephone 1.4 Part 68 of FCC Rules 1.5 Continuity of Service 1.6 Human Factors 1. 7 Ringer Equivalence Number 1.8 Environmental Conditions 1.9 Demonstration of Compliance 2.0 NETWORK COMPATIBILITY 2. 1 Transmission Characteristics Transmit Response Receive Response Sidetone Response Noise Signal Power Limitations Peak Acoustic Pressure Privacy 2,1.8 Features for the Hearing Impaired 2.2 Loop Supervision Characteristics Idle State Originating State Talking State Disconnect Transitions Spurious Off-hook 2.3 Address Signaling General DC Pulsing Dual Tone Multifrequency (DTMF) : :, :,:,~--:>~ Csnter :... :.. r,'...; jlo::eld Road :.\,.r,::in Vi""w, CA 94043

4 Page 2.4 Direct Current Characteristics 2.4.l On-Hook Resistance Off-Hook Resistance Tip-Party Identification 2.5 Alternating Current Characteristics 2.5.l On-Hook Impedance Tip to Ring 2.5.l.2 Tip and Ring to Ground Off-Hook Impedance Balance 2.6 Alerting 2.6.l General l Return Loss Signaling Impedance l Metallic to Longitudinal Longitudinal to Metallic General Application Telephones 2.6.l.2 Selected Application Telephones Bridged Ringing Grounded Ringing 3.0 PHYSICAL CHARACTERISTICS 4.0 SAFETY AND PROTECTION 4. l Fire Prevention 4.2 Electrical Hazard Prevention 4.2.l Maximum Voltages and Currents Fault Conditions 4.3 Mechanical Safety 4.4 Design Standards 4.4.l Materials Grounding Metal Chassis Overload Prote~tion Connections and Wiring Dielectrics Fault Isolation 4.5 Mercury Hazard 4.6 Radiation Hazards 5.0 ELECTRICAL ENVIRONMENT 5.1 Telephone Line Working Potentials and Currents 5.2 Non-Telephone System Potentials and Currents 5.3 Telephone Network Continuity 5.4 Commercial Power Fluctuations

5 PR ELIM INAR Y 6.0 PHYSICAL ENVIRONMENT 6. l Shock Equipment Packaged for Shipment Equipment Unpackaged 6.2 Vibration 6.3 Horizontal Transportation Impact Stresses 6.4 Earthquake Environment 6.5 Storage Environment Requirement Demonstration of Compliance 6.6 Operational Ambient Requirement Demonstration of Compliance 6.7 Thermal Shock Requirement Demonstration of Compliance 6.8 Temperature and Humidity Cycling Requirement Demonstration of Compliance 6.9 Pressure 6.10 Fungus Growth 6.11 Corrosion 6.12 Sand, Dust and Insects 7.0 INTERFERENCE GLOSSARY 7.1 Radio Frequency Interference (RFI) Appendix A References Appendix B FCC Part 68, Subpart D, Cross Reference List Table Table Table Table Table Table Table Table 5.1 Mandatory Transmit Objective Loudness Rating (TOLR) Desirable Transmit Objective Loudness Rating (TOLR) Mandatory Receive Objective Loudness Rating (ROLR) Desirable Receive Objective Loudness Rating (ROLR) AC Impedance Pre-Trip Requirements Acceptable LC Termination Acceptable RC Termination Surge Table Page

6 PR ELIM!NARY LIST OF FIGURES FIGURE l. l l l l l Gl G2 Equipment Interfaces Transmit Frequency Response Receive Frequency Response Weighting Function Response Signal Power Test Circuit - Metallic Signal Power in the 100 Resistive Terminations to 4000 Hertz Band and 3995 to 4005 Hertz Band Signal Power Test Circuit - Longitudinal Voltage in the 100 to Signal Power Test Circuit - Longitudinal and Metallic Voltage above 4000 Hertz Signal Band Weighting Function Percent Break and PPS Limits as a Function of Network Capacitance Percent Break and PPS Limits as a Function of Zener Voltage Required Compensation for Combination Zener Diode and RC 4000 Hertz Band Signalling Interference Test Arrangement Guard Band Weighting Function for Devices which Generate Pulses for Devices which Generate Dial Pulses Network Protection Minimum Impedance During Break Intervals of Dial Pulsing and On-Hook AC Impedance on Frequencies Between 4 and 200 Hertz Dial Pulse Assignments Measurement of Telphone DTMF Keypad Signal Levels Off-Hook Tip to Ring DC Voltage Versus Current Characteristics Dual Tone Multifrequency Tone Power At Originating Staiton Parallel Set DC Characteristics Loop Current Test Circuit Minimum On-Hook AC Impedance - Tip to Ring for Frequencies Between 200 and 3200 Hertz Return Loss Test Circuit Metallic-to-Longitudinal Balance Test Circuit Longitudinal-to-Metallic Balance Requirements Longitudinal-to-Metallic Balance Test Circuit Short Loop False Ringing Detection Circuit Long Loop False Ringing Detection Circuit Combined AC and DC Voltage and Current Limits llb Resistance Lamp Characteristic Surge Generator Circuit Typical Earthquake Synthesized Waveform Earthquake Spectra Criteria Accessibility Probe Loop Simulator Circuit

7 1.0 INTRODUCTION 1. l Purpose The purpose of this Technical Reference is to provide standards containing the information necessary to design and manufacture telephones which are compatible with the Bell System telecommunications network and which will provide service capability consistent with Bell System quality of service objectives for telephone service. This Technical Reference presents criteria which are the minimum necessary to determine if a telephone is technically suitable to be considered for standardization by the American Telephone and Telegraph Co. for use by the Bell Operating Companies. The information in this Technical Reference will be useful to anyone engaged in the manufacture of telephones intended for connection to Bell System facilities and/or equipment and to those purchasing, operating, or using such equipment. The criteria and illustrative test circuits are used to evaluate the compliance of an equipment with FCC Part 68, Subpart D registration rules, its compatibility with Bell System facilities, its potential safety hazards, its performance characteristics and its susceptibility to failure under normal and abnormal environmental conditions. A telephone complies with this Technical Reference if it meets these requirements over the life of the product as specified by the manufacturer. There are two levels of criteria in this document: mandatory (identified by the work 11 shall 11 ) and objective (identified by the word 11 desirable 11 ). The mandatory criteria are generally concerned with safety and protection, signaling compatibility, and absolute minimum acceptable performance levels in such areas as transmission, equipment parameters, and environmental durability. But for the few exceptions which may occur under extreme or unusual circunstances (for example, an unusual circumstance would be one in which a product is shown to comply with the intent of a particular mandatory criterion but does not meet the letter of that criterion), products are required to meet all mandatory criteria in order to be considered technically suitable forrtandardization by AT&T. Objective criteria represent product goals. In some instances these crlteria are included in an effort to assure universal product compatibility, even with the atypical operation of certain Bell System equipment and/or facilities present in statistically small percentages. In other cases objective criteria are presented because th~ir attainment enhances the general performance of the product in all of its contemplated Bell System applications. Where both a mandatory and objective level are presented for the same criteria, the objective 1 evel presents a goal currently identifiable as having distinct compatibility and/or performance advantages toward which future designs must strive.

8 - 2 - This Technical Reference attempts to characterize the telephone interface to the Bell System (see 1.2, Scope) as completely and accurately as possible. However, the electrical characteristics of the equipment and facilities utilized by Bell Operating Companies to provide service in certain locations may differ from the characteristics described herein and facilities described may not be available in all locations. Furthermore, conformance with all the specifications herein will not guara~~ee performance or compatibility in all cases. When cases arise which have not been adequately addressed in this document, the local operating company, equipment manufacturer/supplier, and customer must mutually cooperate to resolve any resultant problems. Criteria of a nonoperational, support nature such as administration and maintenance (documentation, installation, and maintainability) and product manufacture and support (design change classification and control, advice and assistance, training programs, engineering complaint procedures and quality assurance) are not addressed in this document. It should be recognized that technical suitability is only one of many factors which influence a decision to standardize a given product for the Bell System. Market need, economics, and feature content associated with the product also weigh heavily in standardization decisions. 1.2 Scope This Technical Reference addresses the m1n1mum requirements of a generic instrunent which will hereinafter be called the "Basic Telephone Set" having at least a minimum set of generic functions which are necessary and sufficient to provide adequate telephone service. The Basic Telephone Set is also expected to provide the same degree of universality as is presently provided by most current Bell System single line telephones. Therefore, it may be used for either single-party or multi-party service. It may also be used with extensions, or as an extension. (If more than one set is off-hook, the resulting service over the network may not be satisfactory with respect to transmission and sidetone.) While a particular telephone design may perform additional functions to the Basic Telephone Set (such as those automatic functions described in Section 1.3), such functions shall not cause any impairment of the generic functions with respect to these requirements. Conversely, telephones designed for special uses may provide less than the generic functions of the Basic Telephone Set, for example telephones without dials, telephones without ringers or telephones not intended for use on party lines. Since these telephones are not intended to provide the service capabilitie~ of the Basic Telephone Set, the criteria for those generic functions which are not implemented or only partially implemented obviously are not applicable.

9 - 3 - Generally speaking the generic functions of the Basic Telephone Set are: 1. to signify when it is ''on-hook" by presenting an open circuit to the de loop supervisory circuit; 2. to signify when it is ''off-hook" by drawing a certain minimum loop current; 3. to perform a user alerting function when it is on-hook and being called; 4. to provide means for dialing a number to be called; 5. to transduce voiceband acoustic energy to electrical signals for transmission on the loop; 6. to transduce voiceband electrical signals received on the loop to acoustic power; 7. to provide the necessary two port to one port hybrid connection between the above two transducers and the loop respectively; 8. to control the level of sidetone between the transmitting transducer and the receiving transducer; 9. to control the levels of each of items 5, 6 and 8 as a function of the loop loss; 10. to reduce the transmission between both transducers and the loop to an acceptably low level when on-hook, for privacy. In concept, these standards apply to telephones not only as a single instrument, but also to all combinations of a basic instrument and its integrated components, where each combination is intended to be a marketable product. Furthermore, it is not required that every physical telephone entity complies, but that the telephone arrangement, in total, provided for a particular service complies. For example, it may be economical in some cases to provide for compatibility with the extreme of some network parameter (say the upper one percent of loop length) with an optional adjunct. The telephone boundaries are the electrical interface with the network or PBX (tip and ring)~ leads to non-registered equipment, and the acoustic and mechanical interfaces with the user. The telephone may also have an electrical interface with commercial power. These interfaces are shown in Figure 1.1.

10 - 4 - This document is restricted to telephone sets employing a close-speaking microphone and an earphone which permit a single user to carry on two-way, real-time voice communication (handset type telephone). Not included in these standards are telephone features which might be exclusively found in: Emergency telephones Coin telephones Telephones with A-lead control Telephones which contain recording devices for voice or audio information Video and video text telephones Special use telephones such as elevator sets and call boxes Telephones designed for ground start operation Telephones used in data set arrangements Speakerphone-type telephones. 1.3 Definition of a Telephone A telephone is a terminal instrument which permits two-way, realtime voice communication with a distant party over a network or customer premises connection. It converts realtime voice and voiceband acoustic signals into electrical signals suitable for transmission over the telephone network, and converts received electrical signals into acoustic signals. A telephone generates network control signals necessary for originating and placing an outgoing call, or it alerts the user and generates network control signals necessary for answering an incoming call or both. For the purposes of this document, the telephone generates network control signals through the following functions only: l. One or more distinct manual actions which permit origination of an outgoing call (transfer from a steady on-hook state to a steady off-hook state) and generation of the address signals to direct the call to the called party. 2. A distinct manual action which causes cessation of the alerting signal and permits answer of an incoming call (transfer from a steady on-hook state to a steady off-hook state). 3. A distinct manual action which causes disconnection (transfer from a steady off-hook state to a steady on-hook state). 4. A distinct manual action which causes generation of a user controlled duration flash signal (short, temporary tran,ition to an on-hook state during a steady off-hook state). 5. A distinct manual action which automatically causes machine generation of a timed disconnect signal followed by reorigination and redial of the last called number or the dialing of another number.

11 1.4 Part 68 of FCC Rules PRELIMINARY Criteria which are indicated as being requirements under the Federal Communications Commission's Telephone Registration Program are not verbatim reproductions and in some cases only paraphrase the wording of Part 68, Subpart D of Title 47 of the Code of Federal Regulations. In the event that requirements which are more stringent than those in this Technical Reference are adopted in Part 68, the latter take precedence. It is important to note that the criteria of Section C, D and E conform to an AT&T petition (May 10, 1977) to the FCC for a rule change to Section , Signal Power Limitations, and not to the current rule as of the date of this publication. It should also be noted that, whereas this Technical Reference addresses features applicable to party line operation (such as tip-party identification and grounded ringing), Part 68 does not. In addition, the illustrative test arrangements and procedures of this document are not derived from the Part 68, Subpart D rules but are added to the text in an attempt to clarify the intent of the criteria. The illustrative test circuits and procedures in most cases should not be considered as being representative of actual functioning test arrangements but should be viewed as simple illustrations provided to assist the reader's understanding of the rules, nor should it be construed that the illustrative test circuits and procedures are acceptable to, or have been approved by, the FCC for equiµnent registration purposes. Because of the foregoing, equipment designers using this Technical Reference will be required to verify that their products will be in compliance with the most current FCC Rules. Official copies of the rules related to the registration of telephone terminal equipment can be found in Volume II (containin~ Part 2 and Subpart L) and Volume X (containing Part 68 of the Comm1ssion 1 s Rules and Regulations), copies of which may be purchased from the Superintendent of Documents, Government Printing Office, Washington D.C Continuity of Service If a particular design of telephone makes use of commercial or battery power, it shall meet the requirements of the Basic Telephone Set if said power is removed. 1.6 Human Factors Instructions shall be available to the user of customer owned telephones giving simple, concise instructions for all operations of the set with illustrations of controls and indicators, if any, so that use of the telephone as a Basic Telephone Set is facilitated. Dials and controls if any, shall be arranged on the telephone so as to facilitate unencumbered use of the Basic Telephone Set.

12 1.7 Ringer Equivalence Number PRELIMINARY Paragraphs and describe minimum on-hook resistances and impedances that are allowed to terminate a loop in order to assure proper operation of network supervisory and ringing circuits. To allow more than one telephone or a combination of telephones and other devices to terminate a loop, a Ringer Equivalence Number (REN) is assigned to each telephone. This is a weighting factor determined by its relative on-hook loading of the loop as specified in Section (c) of the FCC Rules and Regulations. In no case shall the REN of a telephone exceed 5, nor can the sum of all REN's on a particular loop exceed Environmental Conditions Environmental conditions which can occur during the shipment, installation, storage and use are specified in Sections 5.0 and 6.0. Environmental conditions are presented as being either 11 normal 11 or 11 abnormal 11 Normal conditions are those which are likely to occur to a telephone. Because of this, the Bell System requires telephones to continue to function normally after the application of normal environmental stresses and during normal operating conditions. Conversely, abnormal conditions have a low incidence of occurrence. Equipment designers and manufacturers may find it uneconomical to develop equipment which would continue to function normally after the application of abnormal stresses or during abnormal operating conditions (although it is desirable that the equipment does). Notwithstanding the foregoing, it is required that a telephone continues to comply with the criteria in paragraph 4.0, Safety and Protection, and to all FCC Part 68 requirements after being subjected to abnormal environmental stresses and during abnormal operating conditions. Function normally in this context has a specific meaning: a telephone functions normally when it complies with the criteria as specified in this document including all features and transmission performance requirements. In addition, a telephone that has been subjected to stresses which only occur before or during installation, functions normally if it can be installed by normal procedures and provide the intended service. A telephone that has been subjected to stresses after installation functions normally only if it does not require the attention of a craftsperson to realign it for satisfactory service. It can, however, suffer damage of a cosmetic nature after being subjected to environmental stressing. 1.9 Demonstration of Compliance A satisfactory demonstration of compliance with the criteria specified in this Technical Reference may be accomplished by valid engineering analyses, or laboratory test results, or both.

13 2.0 NETWORK COMPATIBILITY 2.1 Transmission Characteristics 1 n il1M.r\ I The electroacoustic transmission requirements given in this Technical References are based on telephones having a carbon transmitter as currently in general use in the United States. New telephones having design features differing from the above should undergo subjective testing to determine their transmission equivalence to the types in current use. Since methods for subjective testing of telephone sets have not been standardized, they will not be described in this issue Transmit Response A. The transmit response of a telephone is a measure of its acousticto-electric transfer characteristics. To define the transmit response, the output voltage, the frequency response and the equalization over a given range of loop resistances are specified. No attempt is made to specify either transmit linearity or distortion in this standard. B. The transmission level shall be measured in accordance with IEEE Standard * The test circuit of Figure 2B of that standard shall be used. C. The measurement procedure shall also include the following conditions: 1. The battery feed circuit shall be that shown in Figure 2 II in IEEE Standard Measurements shall be made for each of the following loop conditions (Wilcom Products, Inc. Artificial Cable Sections, or equivalent, may be used): a) O kilofeet, b) 9 kilofeet #26 GA AWG non-loaded cable, c) 15 kilofeet #26 GA AWG non-loaded cable. *IEEE Standard "Method for Measuring Transmission Performance of Telephone Sets", obtainable from the Institute of Electrical and Electronic Engineers, 345 East 47 Street, New York, New York

14 The artificial mouth (B & K Instruments, Inc. type 4219 Artificial Voice, or equivalent) shall meet the requirements of Section 4.2 of IEEE Standard However, the artificial mouth output shall be measured at millimeters from the mouth reference plane {lip ring) instead of 7.6 millimeters {0.3 inch). The artificial mouth output shall be adjusted to a sound pressure of db relative to 20 micro-pascals (upa)* for all frequencies-between 180 and 5000 Hz. The zero degree incidence free field response of the microphone shall be used in determining the sound pressure. 4. A level recorder (per Section 4.8 of IEEE Standard ) shall be connected across the 900 ohm load resistor to produce a graph of the frequency response** The horizontal axis shall be frequency (Hz) on a logarithmic scale. The vertical axis shall be in db relative to l millivolt. The recorder shall have a writing speed of approximately 100 db per second. 5. The generator shall logarithmically sweep the frequency range from 180 to 5000 Hz. The sweep rate shall be such that one complete traverse of the 180 to 5000 Hz band requires approximately 10 seconds. 6. The telephone handset shall be mounted in a modal position (per Figure 1 of IEEE Standard ) on a test head designed for telephone measurements (B & K Instruments, Inc. type 4905 Telephone Test Head, or equivalent). The receiver shall be acoustically terminated on the artificial ear. With the handset in the modal position, the location of the microphone relative to the lip ring of the artificial mouth is thus determined by the shape of the handset. *l Pa is equal to 1 Newton per square meter. 20 upa is also the reference pressure for the commonly used term, "Sound Pressure Level (SPL) 11, and is equivalent to 2x10-5 Newtons per square meter, or.0002 dynes per square centimeter. **If the input impedance of the level recorder is less than 50 Kohms, it will effectively lower the value of the 900 ohm load resistor. One solution is to change the value of the resistor so that it in parallel with the input impedance of the level recorder results in a 900 ohm load for the circuit. Alternatively, a high input impedance amplifier with known gain can be inserted between the resistor and the level recorder.

15 If the telephone has a carbon transmitter, the following additional conditions shall also apply: (a) The transmitter shall be conditioned using the procedure described in Paragraph of IEEE Standard prior to the recording of each response curve. (b) Measurements shall be made with the transmitter diaphragm in the 45 face up position to determine compliance with the loudness requirement of Paragraph D and the frequency response shape requirement of Paragraph 2.1.lE. The Transmit Objective Loudness Rating (TOLR) shall be determined for each loop condition in 2 above. Either of the methods described in IEEE Standard * may be used. D. Requirements: 1. The transmit objective loudness rating (TOLR) shall fall between the upper and lower limits as given in Table It is desirable that the TOLR for telephones not limited by present carbon technology have the mean and upper and lower limits given in Table E. The transmit frequency response curves recorded for the O kilofeet loop condition shall fall within the upper and lower limits of the curve shown in Fig The 1000 Hz point on the frequency response curve shall be placed at the O db level in the figure when checking for compliance Receive Response A. The receive response of a telephone is a measure of its electricalto-acoustic transfer characteristics. To define the receive response, the acoustic output or loudness level, the frequency response, and the regulation over a given set of loop conditions are specified. B. The its receive acoustic level shall be measured in accordance with IEEE Standard The test circuit of Figure 2C of that standard shall be used. C. The measurement procedure shall also include the following conditions: *IEEE Standard "Method for Determining Objective Loudness Ratings of Telephone Connections", obtainable from the Institute of Electrical and Electronic Engineers, 345 East 47 Street, New York, New York

16 PR ELIM INARY (l) The battery feed circuit shall be that shown in Figure 2 II of IEEE Standard (2) Measurements shall be made for each of the following loop conditions {Wilcom Products, Inc. Artificial Cable Sections, or equivalent, may be used:) ( a) 0 kilofeet. (b) 9 kilofeet #26 GA AWG non-loaded cable. (c) 15 kilofeet #26 GA AWG non-loaded cable. (3) The artificial ear shall be the IEC coupler for supra-aural earphones per ANSI S , Method for Coupler Calibration of Earphones, instead of the one specified in IEEE Standard The pressure response of the microphone shall be used in determining the sound pressure generated in the coupler by the receiver. (4) The generator shall logarithmically sweep the frequency range from 180 to 5000 Hz. The sweep rate shall be such that one complete traverse of the 180 to 5000 Hz band requires approximately 10 seconds. The generator output shall be adjusted so that the ac voltage across the 10 ohm resistor in the test circuit is -1?. dbv (dbv = 20 log10 voltage). (5) A level recorder (per Section 4.8 of IEEE ) shall be connected to the output of the microphone amplifier for the artificial ear to produce a graph of the frequency response. The horizontal axis shall be frequency (Hz) on a logarithmic scale. The vertical axis shall be in db relative to l Pa. The recorder shall have a writing speed of approximately 100 db per second. (6) A sound attenuating cover (per Section of IEEE Standard ) for the handset transmitter may be required during the recording of the receive characteristics. If the sound pressure measured in the artificial ear with the cover removed and no electrical signal applied to the test circuit is at least 20 db below the 1000 Hz sound pressure with a-12dbv signal applied, the sound attenuating cover is not required. (7) If the telephone being measured uses a carbon transmitter, and if the receive characteristic depends on the transmitter resistance, then the following additional conditions shall also apply:

17 PR ELIM INAR Y (a) (b) The transmitter shall be conditioned using the procedure described in Paragraph of IEEE Standard prior to the recording of each response curve. Measurements shall be made with the transmitter in the 45 face-up position to determine compliance with the loudness requirement of Paragraph 2.l.2E and the frequency response requirement of Paragraph 2.1.2F. D. The Receive Objective Loudness Rating (ROLR) shall be determined for each loop condition in (2) above. Either of the methods descr-ibed in IEEE Standard 661 may be used. E. Requirements: l. The ROLR shall fall between the upper and lower limits as given in Table It is desirable that the ROLR for telephones not limited by present carbon technology have the mean and upper and lower limits given in Table F. The receive frequency response curves recorded for the O kilofeet loop condition shall fall within the upper and lower limits of the curve shown in Figure The 1000 Hz point on the frequency response curve shall be placed at the O db level in the figure when checking for comp liance Sidetone Response A. The sidetone path loss of a telephone is defined as the number of db by which the acoustic output level of the receiver of the telephone, as measured in an artificial ear, is less than the acoustic input level to the transmitter of the same telephone set, as measured at a specified reference point of an artificial mouth. B. Due to the limited information available, requirements concerning this parameter have not been included in this issue. However it should be noted that the subjective evaluation of the performance of a telephone and the loss/noise quality received by a far end party can be influenced by sidetone characteristics of a talker's phone Noise A. Telephone noise is internally generated noise present at the tip and ring terminals of the set. It is defined as the weighted signal power delivered to a specified termination in the absence of an acoustic input to the set.

18 B. The telephone noise shall be measured using the test circuit shown in Figure 8 of IEEE Standard using a noise meter as specified in Sec of IEEE Standard The noise shall be measured with the following amounts of direct current supplied to the telephone: 90 milliamperes 60 milliamperes 30 milliamperes C. When making the noise measurement the transmitter must be isolated from acoustic input and mechanical disturbances. The measurement shall be taken over a period of 5 seconds minimum. If the telephone being measured uses a carbon transmitter the conditioning procedure described in IEEE Standard paragraph shall be performed prior to the measurement and the measurement shall be carried out with the transmitter diaphragm in the following positions: vertical plane 45o degrees face-up face-up face-down D. The telephone noise shall not exceed 15 dbrnc Signal Power Limitations A. Voiceband Metallic Signal Power in the 200 to 4000 Hz Band (1) For internal signal sources not intended for network control signaling, the maximum power of other than live voice signals delivered to a loop simulator circuit of Figure G2 shall not exceed -9 db with respect to one milliwatt, when averaged over any 3 second interval. No manufacturing tolerance is allowed which would permit this power to be exceeded by any unit of equipment. For manually generated tones, this limitation applies to the average power with a 40 percent duty cycle. (21 For internal signal sources primarily intended for network control signaling, the maximum power delivered to a loop simulator circuit shall not exceed one milliwatt when averaged over any 3 second interval, during normal usage. For manually o~i9ina!ed dual tone multifrequency (DTMF) signals, this l1m1tat1on applies to the average power with a 40 percent duty cycle.

19 B. Metallic Signal Power in the 3995 to 4005 Hz Band The maximum power delivered by internal signaling sources (other than those sources intended for network control signaling) in the 3995 to 4005 Hz band to a loop simulator circuit, shall be 18 db below the maximum permitted power specified in (A) above, for the 200 to 4000 Hz band. C. Longitudinal Voltage in the 100 Hz to 4 Kilohertz Frequency Range The weighted root-mean-squared voltage* averaged over 100 milliseconds that is the resultant of all the component longitudinal voltages in this band after weighting according to the curve in Figure shall not exceed the maximum indicated below under the conditions stated in paragraph E below. The weighting curve in Figure has an absolute gain of unity at 4 kilohertz. Frequency Range 100 Hz to 4 khz Max RMS Voltage -30 dbv Longitudinal Terminating Impedance 500 ohms D. Voltages in the 4 Kilohertz to l Megahertz Frequency Range The root-mean-squared voltage* averaged over 100 milliseconds in all of the possible 8 kilohertz bands within the indicated frequency range and under the conditions specified in paragraph E shall not exceed the maximum indicated below. (l) Metallic Voltage Center Frequency of 8 khz Band 8 khz to 12 khz 12 khz to 90 khz 90 khz to l mhz Max Voltage in All 8 khz Bands -( log f) dbv (23-40 log f) dbv -55 dbv Metallic Terminating Impedance 300 ohms 135 ohms 135 ohms where f = center frequency in kilohertz of each of the possible 8 kilohertz bands beginning at 8 khz, and dbv = 20 logia (voltage in volts). (2) Longitudinal Voltage *Average magnitudes may be used for signals that have peak to rms ratios of 20 db and less. RMS limitations must be used instead of average values if the peak to rms ratio of the interfering signal exceeds this value.

20 Center Longitudinal Frequency Max Voltage in Terminating of 8 khz Band All 8 khz Bands Impedance 8 khz to 12 khz -( log f) dbv 500 ohms 12 khz to 60 khz (3-40 log f) dbv 90 ohms 60 khz to 90 khz -68 dbv 90 ohms 90 khz to 1 MHz -62 dbv 90 ohms E. Requirements in paragraphs C and D apply under the following conditions: (1) Equipment shall comply with the limitations when connected to a termination equivalent to the circuit depicted in Figure and when placed in all operating states of the equipment except during network control signaling. (2) Equipment shall comply with the limitations in off-hook states over the range of loop currents that would flow with the equipment connected to a loop simulator circuit. (3) Equipment shall comply with the limitations with a 1000 Hz acoustic signal applied to the electroacoustic transducer that results in a power delivered into the 600 ohm load impedance of 13 dbm. F. Demonstration of Compliance (Paragraphs A-E) The signal power is measured with the equipment in all of its on-hook and off-hook modes and for all values of de loop current that it can draw from the loop simulator circuit. Figure is an illustrative test circuit for estimating the voice band signal power averaged over a 3 second interval. The measurement is made by using a Hewlett-Packard Transmission and Noise Measuring Set, Model 355SB or a Western Electric 3-Type Noise Measuring Set, or the equivalent, when measuring speech signals (these meters do not have a 3 second averaging time, but when used on speech they give a reliable estimate of a 3 second average). While these meters are nearly equivalent, the arrangement of their control switches differ. The control settings on these meters are as follows:

21 Control WESTERN ELECTRIC 3-TYPE NOISE MEASURING SET Setting FUNCTION (Switch) BROG NORM/DAMP (Switch) DAMP WTG (Plug-In Network) 3Kc FLAT HEWLETT PACKARD TRANSMISSION AND NOISE MEASURING SET MODEL.3555B Control Setting INPUT (Switch) NOISE/BROG FUNCTION (Pushbutton) VF/Nm 600BAL NOISE WTG (Switch) 3kHz NORM/DAMP (Switch) DAMP The accuracy of this method can be somewhat improved by increasing the size of the damping capacitance in the Western Elctric 3-Type Noise Measuring Set by 150 microfarads. To do this connect the negative lead of a 150 microfarad capacitor to either terminal of the NORM/DAMP switch and connect the positive lead to ground. This allows the meter to more nearly approximate a 3 second averaging meter. (NOTE: This modification does not necessarily hold for noise meters other than the Western Electric 3-Type.) For non-speech signals a true rms meter such as the Hewlett-Packard 3400A or equivalent can be used to estimate signal power in the voice band. Figure is an illustrative test circuit for measuring longitudinal voltage in the 100 Hz to 4 kilohertz band. The Tektronix model 7L5 Spectrum Analyzer has the capability to average signals over a 100-millisecond interval. Paragraph D specifies voltage limits "in all possible 8 kilohertz bands" within the indicated frequency range. Common laboratory equipments such as the Tektronix model 7L5 Spectrum Analyzer shown in Figure 2.1-6, are not normally equipped with a bandwidth resolution which precisely matches the 8 kilohertz requirement. However, many spectrum analyzers are equipped with a 10 kilohertz bandwidth resolution which is acceptable for assuring compliance with the voltage limitations of this section as long as the equipment under test meets the voltage limitation. Conversely, an equipment which fails the voltage limitation in any 8 kilohertz band will also fail the voltage limitation in the corresponding 10 kilohertz band. Many spectrum analyzers also have the capability to average signals over a 100 millisecond interval. G. On-Hook Signal Power Requirements The power delivered into the loo~ simulator circuit in the on-hook state shall not exceed -55dBm within the frequency band from 200 to 4000 Hz.

22 H. Signaling Interference Requir0'11ents For compliance to these signal interference requirements, the telephone shall either comply with both Paragraphs (1) and (2) below, or shall comply with the criteria of Paragraph (1) during all times and while in all states. (1) Billing Protection /~ During the first 2 seconds after the teleph~transfers to an off-hook state on an incoming call (answer)~if the signal in the 2450 to 2750 Hz band exceeds -55 dbm, the telephone shall not deliver signals into the loop simulator circuit from sources internal to the equipment with power in the 2450 to 2750 Hz band unless at least equal power is present in the 800 to 2450 Hz band. The power of concern in both frequency bands is the power averaged over a 30 millisecond interval. In d0'11onstrating compliance, the 2450 to 2750 Hz band may be defined with a band pass filter having a 3 db point (3 db loss relative to midband loss) at a frequency of 2450 Hz or lower and a 3 db point at a frequency of 2750 Hz or higher. The 800 to 2450 Hz band may be defined by a band pass filter having a 3 db point at a frequency of 800 Hz or higher and a 3 db point at a frequency of 2450 Hz or lower. The midband loss of the filter defining the 2450 to 2750 Hz band shall be less than or equal to the midband loss of the filter defining the 800 to 2450 Hz band. (2) Disconnect Prevention The following criteria apply throughout the entire duration of a call starting 2 seconds after the telephone transfers to an off-hook state on an incoming call (answer). They apply at all times after the telephone transfers to an off-hook state on an outgoing call (origination). The criteria apply to all signals which the telephone may deliver or be caused to deliver (e.g., by a digital sequence) into the loop simulator circuit in all intended applications and modes of operation. The frequency weighted and rectified voltages in the signal band (2450 to 2730 Hz) are compared to the greater of (a) the rectified voltage of a -44 dbm sine wave or (b) the frequency weighted and rectified voltage in the guard band (800 to 2450 Hz) when the rectified voltages are averaged and compared as defined by the configuration in Figure Frequency weighting functions for the two bands are as indicated in the acceptable regions of Figures and The output voltage of the configuration shall not exceed zero more often than an average of once in fifteen minutes. The output voltage of the configuration shall not remain intermittently above zero for an interval of greater than 150 milliseconds in duration more often than an average of once in

23 an hour. The voltage is considered to be intermittently above zero providing that, once it exceeds zero, it does not fall below zero for more than 30 milliseconds (i.e., each interval includes at its end a 30 millisecond interval during which the voltage is continuously below zero). 2.1.n Peak Acoustic Pressure A. The peak acoustic pressure is the maximum telephone handset receiver sound pressure in an artificial ear, resulting from a short high amplitude electrical pulse occurring at the tip and ring terminals of the telephone. B. The peak acoustic pressure shall be measured by applying between the tip and ring terminals voltage surges (one of each polarity) of 800 volts peak, having a 10 microsecond maximum rise time to crest and a 560 microsecond minimum decay time to half crest and measuring the peak acoustic pressure developed in the artificial ear. The test configuration shown in Figure 2C of IEEE Standard may be used, except that all components shown connected externally to tip and ring shall be removed from the configuration before the surge is app 1 i ed. The received acoustic pressure shall be measured in accordance with paragraph except that the sound pressure within the artificial ear shall be measured with a sound level meter having an unweighted "peak hold" mode setting. C. The peak acoustic pressure measured in the artificial ear shall not exceed 130 db relative to 20 upa. (The specified level is higher than desirable. Several subjective studies have shown that customer annoyance when experiencing loud clicks is directly related to the peak level of the clicks. Thus, it is extremely important to set the peak pressure as low as possible, but not so low as to interfere with the peaks of normal speech signals). D. The limiting means shall not distort acoustic signals at pressures below 100 db relative to 20 Pa Privacy It is desirable that the telephones in the idle state not transmit intelligible speech signals to che lines F~atures For The Hearing Impaired A. It is desirable that the telephone provide, or be compatible with, adjuncts which provide a magnetic field for use with hearing aid telephone coils.

24 B. It is desirable that the telephone have a version which is capable of amplifying the receive signal for users with hearing impairments, or be compatible with devices which provide this capability. 2.2 Loop Supervision Characteristics A. Supervisory signals are the means by which a telephone generates a request for service, holds or releases a connection or initiates recall signals. B. Standard call progress signals are given in AT&T Technical References PUB and PUB C. There are four possi~le situations of interest in the supervision of telephone lines; these are 1) idle 2) originating 3) busy and 4) disconnect. 2.2.l Idle State A. This state is characterized by the combination of an on-hook signal and the absence of a connection to the talking path in the central office. The on-hook condition is defined by the on-hook resistance and impedance criteria specified in paragraphs 2.4.l and 2.5.l. B. To limit noise introduced into a connection by an idle (on-hook) telephone on the same line, the power delivered into the loop simulator of Figure G2 shall not exceed 10 dbrnc. C. No de potential shall be transmitted from the telephone to the network Originating State A. This state is characterized by the combination of an off-hook signal and the absence of a connection to a talking path. The off-hook condition is defined by the off-hook resistance and impedance criteria specified in paragraphs and B. Telephones which detect the presence of dial tone shall distinguish between dial tone and noise, where dial tone consists of 350 Hz and 440 Hz (~2%) at a level in excess of -2n dbm (-29 dbm per frequency) measured across a 600-ohm termination at the interface, with a noise level of 40 dbrnc. The maximum expected dial tone level is -?dbm (-10 dbm per frequency). C. If the telephone initiates address signaling without a separate manual action subsequent to the appearance of dial tone, dialing shall commence between 70 milliseconds and 10 seconds after receipt of dial tone. Delays of 10 seconds or more may result in time-out at the central office.

25 D. Spurious opens, other than those due to contact bounce, that cause the loop current to fall below 17 milliamperes for longer than 1 millisecond shall not occur, unless the address signaling sequence is completed. E. The telephone set shall maintain de loop continuity (i.e., maintain the off-hook condition of Paragraph A above and comply with Paragraph D above) regardless of the polarity of the serving loop Talking State A. This state is characterized by the combination of an off-hook signal and the connection to a talking path. The off-hook condition is defined by the off-hook resistance and impedance criteria specified in paragraphs and B. During this state, a telephone which has originated a call Shall not generate an on-hook indication longer than 100 milliseconds in duration, except to disconnect or for flash signaling. C. A telephone which has answered an incoming call shall not generate an on-hook signal longer than 10 seconds except to signal a disconnect request. D. If flash signaling is generated automatically, the telephone shall generate an on-hook indication of 300 milliseconds to 1 second to signal a flash request. E. Continuity of de loop current is not guaranteed, therefore the telephone shall not depend on such continuity for proper operation. Loop current interruption shall not cause the telephone to make a transition from one state to another Disconnect A. This state is characterized by an on-hook signal during a connection to a talking path. The on-hook condition is defined by the on-hook resistance and impedance criteria specified in paragraphs?..4.1 and B. A telephone with a re-dial button that provides a disconnect signal shall go on-hook for at least 1.5 seconds prior to re-origination Transitions A. Transitions from the on-hook state to the off-hook state shall not activate the telephone receive path prior to application of the station set circuitry to the loop.

26 B. The loop current through a telephone when connected to a loop simulator circuit with the 600 ohm resistor and 500 microfarad capacitor therein disconnected, shall, for at least 5 seconds after the telephone goes to the normal off-hook state which would occur in response to ringing shall meet either of two conditions: (1) be at least as great as the current obtained in the same loop simulator circuit with a 200 ohm resistance connected across tip and ring in place of the telephone, or (2) not decrease by more than 25 percent from its maximum value attained during this 5 second interval; unless the telephone is returned to the on-hook state during the above 5 second interval. C. Demonstration of Compliance A telephone which has an off-hook tip to ring de resistance of 200 ohms or less satisfies this requirement. Otherwise, the decrease in loop current during the first 5 seconds after the equipment goes off-hook is measured by using the illustrative circuit of Figure 2, Spurious Off-Hook An idle telephone shall not cause spurious off-hook signals of greater than 6 milliseconds. 2.3 ADDRESS SIGNALING General Addressing shall not be by means of a mixture of de pulses and DTMF pulses during any single call origination DC Pulsing NOTES: 1. The following standards apply for loop current as measured through a nonreactive load on tip and ring. 2. The following criteria insure that dial pulses generated by a telephone are compatible with dial pulse receivers. These requirements apply to both mechanical and semiconductor dialers. Failure to meet the following criteria can cause improper registration of digits, missed digits or pulse splitting. This can result in misdirected calls, time-outs, and other undesirable effects. The following requirements apply when dial pulses are generated by equipment with a dial pulsing contact bridged by a passive RC contact protection network